On UVR and CVR units, the under voltage relay de-energises if any of the phase to neutral input voltages fall below the ‘set volts’ level. The relay does not energise (or the UVR LED light) until all phase to neutral voltages are restored to above the set volts plus the (adjustable) differential voltage.

On OVR and CVR units, the over voltage relay de-energises if any of the phase to neutral voltages rises above the ‘set volts’ level. The relay does not energise (or the OVR LED light) until all the phase to neutral voltages return below the set voltage minus the differential voltage. The over voltage relay also de-energises on total loss of supply.

On PFR units, two phase voltages are compared with the third phase. The relay de-energises if either phase to phase voltage falls below the set level. The relay does not energise until the phase to phase voltages rise above the set volts level plus the (fixed) differential voltage. On ‘R’ option units, the relay only energises if the correct phase sequence is connected.

Electrical connection to all units is via screw terminals (accepting stripped wires or narrow blade crimps). Each unit has a robust polycarbonate casing, designed for DIN rail or surface mounting.